Television apparatus



March 30, 1937. G. SCHUBERT ET AL TELEVISION APPARATUS 2 Sheets-Sheet 1 Filed Nov. 3, 1932 Fig.1

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I IA J I March 30, 1937.- s. SCHUB'ERT ET AL TELEVI S ION APPARATUS Filed Nov. 3, 1932 2 Sheets-Sheet 2 Patented Mar. 30, 1937 UNITED STATES PATENT OFFICE TELEVISION APPARATUS Application November 3, 1932, Serial No. 641,092 In Germany November 5, 1931 7 Claims.

Television transmission apparatus of the kind hitherto known fulfil merely the requirement for analysis or decomposition either of normal positive films with the assistance oi! so-called 5 kinematograph transmitters or of the representation of spacially disposed objects or persons with the assistance of so-called light-ray scanning transmitters, and for the purposes of transmission after conversion into electrical im- 1 pulses.

Individual experiments have also been conducted in connection with scenes making use of daylight or artificial illumination. However, with consideration to the existing state of the 5 art, allowance must 'be made in the case of a relatively large number of image points for an intensity of light in the illumination of the scene to be transmitted such as might be provided only by the sun. Transmissions of this nature have hardly been possible heretofore in the case of dull weather or other adverse conditions of light. From a theoretical standpoint it is certainly possible to also fulfil more elaborate requirements by the use of more extensive means. Nevertheless it would hardly seem possible to limit the dimensions of the apparatus to an acceptable extent, and above all to obtain a recording and transmitting apparatus of a portable kind. This constitutes a considerable drawback which is still revealed by all television transmission methods hitherto proposed, it thus being made impossible to transmit topical occurrences of any kind, such as football matches, regattas, receptions, etc.

The single possibility of transmitting topical occurrences, as provided according to the existing state of the art, consists in filming the same, making from this film positive copies, and then performing transmission with the assistance of a kinematograph television transmission means.

This method naturally represents nothing more than a kinematographic report conveyed with the assistance of a television apparatus and has little to do with television proper, as the interval between the occurrence to be transmitted and the reproduction amounts under existing conditions to a matter of hours or, generally speaking, even days.

To overcome these limitations there has been evolved according to the invention a method of transmission, in which there is first made of the scene to be transmitted a normal film, which immediately following undergoes the normal developing, fixing, washing and drying process, and

after completion is analyzed or decomposed as negative film at the point of operations by means of a kinematograph transmitter, and then transmitted. Furthermore, in accordance with the invention, the copying process is dispensed with, so that it is possible to transmit the image or picture within a period of at the most one hour following the recordal.

An additional feature of the invention resides in the fact that in order to still further diminish the elapse of time between the kinematographic recordal and the television transmission the film may be analyzed or decomposed immediately following the development, possibly with the inclusion of a preliminary fixing process, fixing, washing and drying then being performed after the analysis or decomposition has taken place.

Careful experiments have shown that with the assistance of special developers, and more particularly those of a strongly alkaline kind, the time for developing may be reduced to very brief periods, say 2 seconds, inasmuch as it is not absolutely essential to develop the film in such fashion that the same provides an excellent negative such as required in connection with a normal film copy. It is merely necessary for the negative. to reveal sufficient contrast between light and dark that the photo-cell is provided with sufficient fluctuations in light during the scanning of the film, and the amplifier furnished with an input energy of such extent that the same is situated well above the level of disturbance occasioned by other effects and influences.

This method would accordingly enable occurrences just taking place to be transmitted to subscribers with a delay which amounts to a few seconds. Certainly it is hardly practicable in the case of this method to make use of the normal scanning processes. The same consist in the fact that the film gate through which the film moves is lighted in its full expanse, and that the image is projected on to the. perforated disc, behind which there is arranged the photocell. In the method according to the invention, when employing a film which has not been fixed, care must be taken that the film, by reason of the scanning process, is not additionally darkened, or only to such slight extent that the. differences between light and dark are still maintained as such.

According, therefore, to the invention, there will be employed as far as possible for the purpose of recordal a film, the maximum sensitiveness of which is situated in another part of the spectrum to the maximum sensitiveness of the light-responsive cell. Thus, for example, when employing a blue-sensitive film, it will be desirable to perform scanning with a red light, for which particularly calsium cells are very sensitive, there being included, for example, a red filter between the light source and the film. A further possibility of avoiding additional darkening consists in lighting on each occasion only that part of the film image which corresponds with one size of image point, this being accomplished by lighting the image recess in the perforated disc in its full expanse, reproducing the perforated disc on the film by means of an objective, and arranging the photo-cell behind the film. The film and the perforated disc accordingly change places as compared with the known arrangements. The darkening which is possible at all in this method amounts in comparison with the normal process to the fraction derived from the number of image points. Naturally it may be desirable to combine the two methods, and to perform scanning with a red bundle of rays of the cross-section of the image point conducted line by line over the film.

Since, as already stated, the film, in the method according to the invention, is passed through the scanning apparatus in a wet condition, it is desirable not to employ a normal film projector with intermittent movement, as in this way considerable demands would be imposed on the film with regard to mechanical strength and elasticity, the film, in accordance with the invention, being passed through the scanning apparatus at a constant speed.

In order with this method to permit of scanning line by line there is employed in place of the normal Nipkow disc, in which the scanning apertures are located about a spiral, a scanning element in which the scanning apertures are situated in a circle which is concentric to the axis of rotation. Upon rotation of this disc, which is lighted by a source of light, and is reproduced on the film, an intensive spot of light of the expanse of the so-called image point is conducted line by line over the film vertically to the direction of movement thereof. If new it is desired to scan successively line by line the complete image on the film, the arrangement requires to be such that in the same time in which the, say, square spot of light has traversed one line on the film the latter is advanced to the extent of the width of the line, i. e., the length of the edge of the assumedly square spot. It is obvious that upon the co-operation of these two movements the scanned line on the film is not exactly vertical to the direction of movement of the film, but together therewith encloses a certain angle which, however, is so small that upon the reproduction with a normal Nipkow disc any appreciable distortion is not to be expected on account thereof. Naturally a constant predetermined ratio requires to exist between the angular velocity of the scanning disc, i. e., the rate of movement of the beam of light over the film, and the continuous rate of feed of the film, whereby the phase between these two movements also requires to be maintained constant. This is accomplished either by operation with synchronized motors or, in the most elementary form, by mechanical coupling.

An additional advantage associated with the method according to the invention resides in the fact that the energy radiated by the source of light is utilized to a considerably better extent, as on the scanning disc there requires to be lighted merely a surface which corresponds with one line. In consequence there may be employed a source of light having a heated filament.

If under adverse circumstances it is not possible to perform one of the above methods, say, the scanning operation, with a light of that kind which does not fall within the range of sensitiveness of the photographic emulsion, it may be desirable to slightly fix the film after the development, and fix the same finally after the scanning operation.

Although in the film the contrast between light and dark is such as to suffice for the scanning and transmission of a television image, it may nevertheless be desirable for subsequent optical reproduction to employ a better developed negative. In this case there would be included after the scanning operation an additional developing process, and preliminary fixing would be dispensed with.

The film, after passing through the developing bath, and possibly also the preliminary fixing bath, is conducted in direct fashion through the scanning device, in which it is traversed by a bundle of rays. Upon this scanning process any drops of water possibly adhering to the film as a result of the development might naturally give rise to disturbances. Under certain circum stances, therefore, it may be desirable to remove the drops of water, or also the complete coating of moisture, from the film before the latter is conducted through the scanning device, use being made of a rapidly acting drying process.

This may consist in drying the film in a current of hot air, or passing the same through a bath of alcohol and then drying, or in removing the drops of water by a scraping device. The drops of water might also be removed by the inclusion of a rearwardly moved compensating loop between the developing and the scanning means, or the different methods might be suitably combined.

The lapse of time between the actual recordal and the scanning operation is to be reduced to all possible extent, as already stated. The same depends solely on the length of the film between the exposure window and the scanning window or gate and also on the rate at which the film is moved. It will accordingly be desirable to place the recording apparatus and the scanning apparatus as close together as possible, and to include the developing process between the two. The film, therefore, is preferably passed in direct fashion from the recording apparatus to the developer, and after leaving the developing bath is conducted immediately through the window of the scanning device. The time for which the film requires to remain in the developer cannot be reduced beyond a certain extent. It is accordingly merely a matter of making as short as possible the lengths of film which are situated on the one hand between the recording window and the developer and on the other hand between the developer and the scanning window. Since generally speaking operations are performed with a fixed number of image changes, i. e., a fixed number of film images are taken per second and are scanned in the scanning apparatus, it would appear desirable in this connection to increase the rate of movement of the film, which might be accomplished by employing a larger film image.

This, however, is accompanied by the disadvantage that the length of film which requires to be accomodated in the developer is relatively large. The difficulties occurring in this connection should not be under-estimated, as the wet fixed, washed and dried and then wound.

film requires under all circumstances to be handled very carefully and so guided that the emulsion is not damaged. The film, therefore, requires to be guided merely laterally, or in such fashion that the same at the middle enters intocontact with guide or feed rolls only on the celluloid side. For this reason it is accordingly desirable to employ a small size of image. Thus, for example, the length of film which must be introduced into the developer amounts in the case of 25 image changes per second and when employing a narrow film 7 mm. in the upright direction, assuming the time for development to be 2 seconds, to only approximately 35 cm. It will be obvious that even when employing a normal kinematograph film 8 millimetres in height it will still be possible to accommodate the requisite length of film in the developing bath.

At this point it may be mentioned that the film should not be guided in a tensioned state between recording apparatus, developing bath and scanning apparatus, as generally speaking it will not be convenient to attain synchronous drive of these three apparatus by a mechanical coupling. If, therefore, synchronous motors are employed phase displacements arising from fluctuations in load and potential are not to be avoided. The compensating loops should accordingly be so calculated that the maximum phase displacements occurring may still be compensated.

Importance must also be attached to the guiding of the film when passing the scanning window or gate so that the wet film is moved exactly in a plane, as otherwise there would be no exact optical reproduction, which in, turn would result in lack of sharpness in the succession of lines. The film, therefore, is preferably conducted over two closely disposed transport rolls, the axial spacing of which is so calculated that the distance between two corresponding teeth is a multiple of the spacing of the perforations, so that the film is properly tensioned.

It would naturally also be conceivable to perform the advance movement of the film by only one transport drum, moved into connection following thescanning process, and to pass the film closely in front of the same through a clamping device, the pressure of which is so calculated that the film is lightly tensioned. This clamping device might be constructed simultaneously to act as scraping device for any particles of water still adhering.

After the film has passed the scanning device the same is again developed as required, or finally In various apparatus, particularly if the same are of a portable kind, it will be desirable, for the sake of economy in space, not to subject the film to additional chemical treatment following the scanning operation, but to wind the same on to a suitably constructed storage drum. Dependent on the chemical process performed prior to the scanning operation, a brief final fixing will be included or an interrupter bath employed. The

, storage drum for reception of the wet film requires to be constructed accordingly.

The film will accordingly be applied to a spiral of such pitch that adjacently disposed pieces of film cannot touch, the film, for example, being placed in a spirally constructed groove, or being wound with the interposition of two distance bands, which cover only the side edges of the film. The entire spool is preferably located in a drum filled with water. The film thus stored may be additionally treated later for other purposes.

Since the film naturally requires to be moved at the same speed by each transport drum, all transport drums serving to advance the film require to be driven synchronously. It might, therefore, appear possible to mechanically couple all transport drums. This method, however, presents difliculties insofar as by reason of the neces sary mechanical transmission members, such as gear wheels, small fluctuations in load and retarding effects might take place, which in turn would variously load the synchronous motor and thus vary its phase position. This variation in the phase position, assuming the same is not of such extent as to destroy the synchronism of the motor, causes a displacement of the image at the receiving end. The principal point concerned is that the scanning operation takes place perfectly synchronously. The fact as to whether the remaining apparatus are operated with exactly constant phase is not of considerable importance. Various synchronous motors will therefore be employed. The one will be used for driving the scanning apparatus, and another for operating the remaining part apparatus. If now the phase position between these two motors is somewhat displaced, this is in no way disturbing, since, as stated above, small compensating loops are included for this purpose.

Figure 1 is a line diagram of a transmitter.

Figures 2 and 3 are an elevation and a side view of developing tank 4 of Figure 1.

Figure 4 shows the scanning device used at the transmitter.

A very convenient form of embodiment of the invention is illustrated in purely diagrammatical form in Fig. l of the drawings. In this case I is the camera for making the photographic recordal, to which camera the film 2 is fed from the stor age drum 3. The film 2 moving in the direction of the arrows passes after exposure into the apparatus 4, in which the same is subjected to a preliminary chemical treatment, whether for the purpose of mere development or for development and fixing. The film thereupon passes to the scanning device 5, and after leaving the same is taken up by the spooling device 6.

Figs. 2 and 3 show a possible form of embodiment in respect of the apparatus 4, Fig. 2 being a front elevational view and Fig. 3 a side elevation. The trough 1, which is filled with developer, contains two rolls 8 and 9, which are connected with each other through the medium of the gear wheels H) and H and a chain I2, and are operated in common by the synchronous motor through the medium of the gear wheel I3. Beyond this there are mounted at each of the two ends of the roller 9 two rims having teeth l4, over which the film is now conducted in the manner indicated in the drawings. At the point of the teeth M'the film is pressed lightly against the rolls 8 and 9 by two pressure rollers l 5. The film is introduced in such fashion that the sensitized face is situated towards the outside. The rolls 15 are so constructed that the same press the film against the rollers 8 and 9 merely laterally in the vicinity of the perforations.

In Fig. 4 there is shown a convenient arrangement of the scanning device in cross-section. The filamentary light source l6 situated vertically in the plane of the drawings lights through the medium of a condenser system ll that part of the scanning disc l8 which is traversed by the scanning apertures situated in a circle concentrically to the axis of rotation l9. The scanning apertures are reproduced on the film 2 by means of the objective 20. The film is held in a tensioned condition between the two transport drums 2| and 22. Beyond this there are also provided two pressure rolls 23 and 2G. The light falling through the film traverses the lens 25 and then strikes the light-responsive layer of the cell 27. The fluctuations in current supplied by the photo cell are conducted in the usual manner to an amplifier. The lens 25 is preferably so arranged and also possesses such optical data that it reproduces the objective 28 on the layer 26. Should it be found desirable, a light filter may be provided in the path of the rays, preferably in the vicinity of the condenser system H. The transport drums 2| F and 22 on the one hand and the scanning disc F8 on the other hand are mechanically coupled with each other with a certain transmission ratio and are driven by a synchronous motor; or alternatively separate synchronous motors may be employed for each of the two operating elements. In the embodiment referred to it has merely been stated up to now that as analyzing element there may be employed a Nipkow disc or a scanning disc in which the apertures are situated in a circle concentrically to the axis of rotation. Naturally other equivalent means may be employed, for example Weills reflector wheels or other refiectory wheels, the refiectory faces of which are situated parallel to the axis of rotation.

When employing the method as described difficulties will at first be encountered assuming together with the image it is also desired to transmit the sound, since between sound and image a difference of a few seconds is not to be avoided.

Upon reception the sound would accordingly precede the image to the extent of this difference. This fact might certainly be accepted as inevit able assuming merely explanatory words were spoken in conjunction with a certain transmission. In the majority of cases, however, it will be desirable to preclude this chronological difference. This may be accomplished in relatively simple fashion by artificially delaying the transmission of the sound to the same degree as the transmission of the image.

According to the invention, the sound may for this purpose be fixed according to one of the known sound-recording processes, and transmitted with corresponding delay simultaneously with the image. Thus, for example, it is possible on the film serving for transmission of the image to simultaneously record the sound according to one of the known light-sound processes and to transmit the same together with the image, whereby synchronism between sound and image is of necessity obtained automatically. The sound might equally well be recorded on a second, separate film. The first method, however, ofiers greater advantages with regard to synchronization. The sound strip is developed together with the image strip, and since the same is treated according to the same process, for example, has also not been fixed, or merely preliminarily fixed, it requires to be illuminated with red light. Another method consists in recording the sound in the known manner on a steel wire, and performing transmission synchronously with the image.

Certain difficulties also present themselves with regard to transmission of the images from the direct point of recordal to the wireless transmitter passing the images to subscribers. The most simple possibility of communicating the images via cable or free lines would hardly enter into the question in the majority of cases, since on account of the large frequency band widths both wires as well as cables do not adapt themselves to the transmission of television images. These difficulties, however, may be overcome according to the invention by transmitting the images to the main transmitter by means of a light portable ultra-short wave transmitter, the main transmitter then taking over the transmission of the images to subscribers. The sound may naturally be passed to the main transmitter by special cable, as usual in the case of radio transmissions of the ordinary kind.

It will be understood that no limitation is made to the specific forms of embodiment referred to in the above and illustrated in the drawings, but that various modifications are quite possible within the meaning of the above description and the annexed claims without departing from the spirit of the invention.

What we claim as new and desire to secure by Letters Patent is:

1. In a method of electrically transmitting animated pictures, scenes and the like, in which a light sensitive cell and a scanning device is employed, the steps of exposing a blue-sensitive moving picture film to the object whose image is to be transmitted, conducting then said blue-sensitive film immediately through a developing bath adapted to form images which, though of insufficient contrast for satisfactory photographic reproduction are capable of controlling the light sensitive cell, and then scanning the images on said film, the scanning being effected with red light to which the film is insensitive.

2. In a television system for transmitting photographic images, a developed but still light sensitive film carrying said images, said film having its maximum sensitiveness to light over a predetermined band of wavelengths, and means for successively scanning elementary areas of said film to produce a television signal, said means including a source of light having a wavelength lying outside the range of said predetermined band.

3. In a television system for transmitting photographic images, an undeveloped film carrying said images and having an emulsion thereon of. maximum sensitivity to one portion of the light spectrum, means for applying a developing agent to said film, and means for successively scanning elemental areas of said developed film with light corresponding to a different portion of the spectrum, while said film is still light sensitive, to produce a television signal.

4. In a television system for transmitting photographic images, an undeveloped film carrying said images and having thereon an emulsion with maximum sensitivity to light in the range of 0422-0492 microns, means for applying a developing agent to said film, and mean for successively scanning elemental areas of said developed film With light in the range of 0.64'7-0.800 microns, to which said film is relatively insensitive, while still light sensitive, to produce a television signal.

5. The method of generating television signals which includes the steps of exposing a motion picture film to photograph the image to be transmitted, partially processing said film to develop said image, scanning said film by illuminating one picture point thereof at a time while still sensitive to certain wave lengths of light, with a wavelength band to which the film is relatively insensitive, and varying an electrical current in response to the light transmitted by said film to generate the required signal.

permanently recording changing scenes which includes the steps of exposing a motion picture film which is sensitive to a limited band of wavelengths to photograph such scenes, partially processing said film to develop and fix the latent images thereon, scanning said film with light of wavelengths to which said film is relatively insensitive while said processing is incomplete and the film is still capable of being afiected by wavelengths of said first-mentioned band, and. then 10 carrying said processing to completion.

GEORG CHUBERT. ROLF MOLLER. 

